The invention relates to a godet for guiding at least one advancing yarn as part of a yarn processing operation, and which utilizes one or more radially operative magnetic bearings.
A godet of the described type is disclosed in DE 197 33 239 A1. In this prior godet, a hollow-cylindrical godet casing is magnetically mounted on a projecting support. To this end, a plurality of radially operative magnetic bearings are provided, which are basically formed by a rotating part and a stationary part. In this connection, one needs to distinguish between a passive magnetic bearing and an active magnetic bearing. The invention relates to the active, radially operative magnetic bearing, wherein the stationary part of the magnetic bearing is formed by at least one pole element, which mounts one or more windings. The pole elements include pole ends, which face the rotating part of the magnetic bearing in a bearing gap.
In the known godet, the rotating part of the magnetic bearing is formed by a shaft connected to the godet casing, or directly by the godet casing. In this case, the materials of the shaft or the godet casing must be of such a quality that a closed magnetic flux develops between the pole ends. This makes it necessary to select the materials for the shaft or godet casing, while taking into account a magnetization, and to consider the requirements for meeting the component functions. A further disadvantage of the known godet lies in that hysteresis losses or eddy current losses as well as possible leakage losses occur during the transition of the magnetic flux into the shaft or the godet casing. Such losses must be covered, if need be, by the driving power of the godet drive.
Likewise, the godet as disclosed in EP 0 770 719 A1 has similar disadvantages. In this case, the pole ends directly face the rotating components of the godet with a bearing gap.
It is an object of the invention to improve a godet of the initially described type by means of radially operative magnetic bearings such that the lowest possible losses occur in the magnetic bearings.
A further object of the invention is to minimize a mutual influence of the rotating components of the godet with the parts of the magnetic bearing.